items question

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this photo isnt mine, and i find a lot of these great designs online.
my question is:
this person used partitions obviously on the right and left of the photos to indent the wooden partitions to make bookshelves; and used the underwater wall as a background in the center.
in the center of the photo on both sides upper and lower there are blocks that have holes in them. there is a space in between them vertically, allowing for the showing of the wallpaper.
i have no idea what those 'blocks with holes in them' item(s) are, and how to arrange the interior to create the decor. what are the block items?

 

[Clock]

The blocks with holes item is a custom design for the glow in the dark stickers. I don’t know the pattern code, but for sure those patterns are used for the glow in the dark stickers DIY.

 

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thank you so much!!